Method of producing fabrics for crease-retaining garments



United States Patent 3,450,484 METHOD OF PRODUCING FABRICS FOR CREASE-RETAINING GARMENTS John M. Ross, Jr., Brunswick. N.J., and Daniel A.Lima, Glen Burnie, Md., assignors to FMC Corporation, New York, N.Y., acorporation of Delaware N Drawing. Filed Aug. 9, 1965, Ser. No. 478,417

Int. Cl. D06m 13/14 US. Cl. 8116.3 3 Claims ABSTRACT OF THE DISCLOSUREThis invention relates to the production of crease-resistant fabrics ofthe so-called deferred cure type, in which final cure of thecrease-resisting fabric finish is delayed until after articles are madefrom the fabric, so that permanent creases can be made in the articles,and has as its principal object the elimination of the odor problemwhich has heretofore arisen with these materials.

Crease-proofing of cellulosic fabrics is an old art. Many years ago, itwas discovered that if such a fabric was impregnated with awater-soluble thermosetting resin, and the resin cured on the fabric, afinish was obtained which gave materials which were resistant tocreasing. Originally, the useful finishes were the heatconvertibleresins, made by heating amino compounds like urea, melamine, biuret,ammeline, etc., with formaldehyde. More recently, it was discovered thatcellulose itself would react with certain finishing agents which werenot in themselves resins, and would not form resins on simply heatingalone. Of these materials the condensation products of the lower alkylcarbamates andformaldehyde have proven the most promising, in particularthe condensates of formaldehyde with methyl carbamate and ethylcarbamate.

In the development of these crease-resistant fabrics, a recentcommercial development is the so-called deferred cure process. In thisprocess, fabric is impregnated with the crease-resistant finish, and thefabric is dried very carefully to prevent premature cross-linking of thefinish. Cross-linking of the finish is deferred until after the fabricis cut up and made into articles such as garments; the desired creasesare pressed into the garments, the heat of the pressing irons acting tofurther cross-linking, with final cure of the finish coming afterpressing. The method has been suggested for both amino-formaldehyderesin finishes (see Warnock et al., US. Patent 2,974,432, issued Mar.14, 1961) and for cellulose-reactive finishes of the alkylcarbamate-formaldehyde type (see Kullman et al., American DyestutfReporter, Mar. 2, 1964, pages 22 and 23).

While the deferred cure process is technically sound, it has one veryimportant disadvantage. Both the aminoformaldehyde resin finishes andthe alkyl carbamateformaldehyde finishes contain loosely boundformaldehyde which splits off during the final curing, and makes workingwith these finishes most unpleasant in the absence of good ventilation-aconvenience notably lacking in many lofts in which garments arefinished. Deodorants have therefore been widely used in the formation ofdeferred cure finishes. However, this adds to the cost, and ends up bymerely masking the problem as well as the odor. In many shops, thedeodorized finish odors prove just as objectionable as formaldehyde.

We have discovered that the odor problem can be eliminated in deferredcure processing of cellulosic fabrics with alkyl carbamate-formaldehydefinishes, by the very simple expedient of drying the fabric to amoisture content of from about 4.75 to about 3%. This is actually belowthe equilibrium moisture content of cotton under typical ambientconditions, e.g., 5.0% at F. and 40% relative humidity. Surprisingly, itappears at this point that just sufficient cross-linking has occurred tofix any unvolatilized formaldehyde to the cellulose without going to thepoint where the desired advantages of conventional fully deferred curingare lost. This is directly contrary to the teachings of prior artinvestigators who have always retained a substantial amount of moisturein their fabrics, in order to prevent substantial cross-linking beforeprocessing into clothing.

It is even more surprising that our new method is applicable in thepractice of the invention taught in our copending application Ser. No.368,362, filed May 18, 1964. This application teaches the use of a pHrange of about 2 to 4 in the fabric treating bath, which acceleratescure and produces a fabric of improved strength because of the milderconditions to which the fabric has to be subjected during the cure.

In the practice of our invention, we may use any of the lower alkylcarbamates, including methyl, ethyl, n propyl, isopropyl, and sec-butylcarbamates. The methyl, ethyl, and isopropyl carbamates are preferred.

Alkyl carbamates are commercially available products which may beprepared in various ways which are well known to those skilled in theart. Typical processes for preparing alkyl carbamates are described inUS. Patents 3,013,065 and 3,013,064. These carbamates are generallyprepared by dissolving urea in the corresponding alcohol up to thesolubility limit of urea in alcohol. Alkyl carbamates may also beprepared by the reaction of ammonia and an alkyl chloroformate.

The alkyl carbamate-formaldehyde condensates used herein may be preparedin accordance with well-known techniques by reacting 2-3 moles offormaldehyde with each mole of alkyl carbamate in aqueous medium at a pHof 210.5. The pH is controlled by the addition of a basic material suchas sodium hydroxide, sodium carbonate, barium hydroxide,triethanolamine, etc. The reaction will take place by standing overnightat room temperature, or by mildly heating for a shorter period of timesuch as 45 C. for two hours. The reactioninitially takes place to theextent of condensing about 1.5-1.6 moles of formaldehyde with each moleof carbamate and the excess formaldehyde remains dissolved in theaqueous medium. When the reaction equilibrium is reached, the condensateis stabilized by lowering the pH to about 7 by the addition of acid suchas hydrochloric or acetic. The specific method by which the condensateis prepared is not critical to the success of this invention.

The impregnating solution, which is often called the pad bath, isprepared by adjusting the concentration of the active material (i.e. thecarbamate-formaldehyde condensate) in the aqueous medium to about 230%,and preferably about 812%. Magnesium chloride hexahydrate or othercatalyst is then added in a concentration which may vary from about10100% by weight, based on the condensate, and preferably about 25-40%.

The impregnating solution may be used as such, but it preferably isadjusted to a pH of about 2 to 4, and preferably about 2.5 to 3.5, astaught in our copending application Ser. No. 368,362, filed May 18,1964. As indicated there, substantially any organic acid may be used forthe adjustment.

Ordinarily there is added to the impregnating solution a conventionalsoftenere.g., dispersed low molecular weight polyethylene, various fattyacid derivatives including quaternary ammonium and amidederivatives-which acts to give the fabric a soft, pleasant feel. Wheredesired, a hand builder is also often added, to give body and firmness;typical hand builders are polyvinyl acetate and modified starches.

Any type of cellulose textile material may be rendered wrinkle-resistantin accordance with this invention. Suitable textile materials includenatural cellulose products such as cotton, linen, hemp, flax, ramie,sisal, jute, straw, and wood; regenerated cellulose products such asviscose, cuprammonium, and high tenacity-modified viscose rayons. Thecellulose textile may be in the form of a fiber, tfilament, or yarn orit may be in the form of a paper or cloth made by weaving, felting,knitting, knotting, bonding, or crocheting. The cellulose material mayalso be in admixture with other natural or synthetic fibrous materials,e.g., the conventional 65 polyester fiberz35 cotton blend used in manyfabrics.

The impregnated textile, after being impregnated with the desired amountof finishing agent, is now dried, in accordance with this invention, toremove the free moisture to between about 4.75 and 3%, i.e., below thenormal equilibrium content of free moisture at ambient conditions. Thisrequires a time-temperature cycle which starts the cross-linking andeliminates not only the free water but all the formaldehyde which willcome off. Temperatures of from about 95 to 120 C. are preferred, withtimes of three to ten minutes, the lower temperatures requiring thelonger times. Temperature of the order of as high as 150 C. for a fewseconds can also be used, but the resultant moisture content gets moredifficult to control as the temperature goes up. Strangely enough, thepresence or absence of organic acid in the impregnating solution haslittle or no effect on the permissible moisture content; it appears thatthis acid produces most or all of its effect in the final stages of thecure.

The cellulose textile fabrics prepared in this manner can be stored asneeded for considerable periods of time, then made into garments orother objects, and after-cured after the desired creases are pressedinto the garments, as is conventional in the deferred cure process.However, with the process of this invention, no substantial formaldehydeodor is developed in after-curing, so that the textiles may beconveniently used under any conditions of ventilation.

The following typical examples of the invention are given by way ofillustration and not by way of limitation; they can be multipliedindefinitely without departing from the scope of the invention asdefined in the claims. In the examples, all parts are by weight.

Example 1.-Preparation of ethyl carbamate-formaldehyde condensateEighty-nine parts of ethyl carbamate and 202 parts of 37% formaldehyde(methanol-free) (molar ratio of carbamate to formaldehyde 1:2.5) werecharged into a vessel equipped with a stirrer, thermometer, and heatingand cooling coils. The pH was adjusted to 105:0.1 with 50% NaOH. Theexothermic reaction raised the temperature to 35-40 C. within an hour;thereafter the mix was maintained at 3842 C. for about an additionalhour, until the free formaldehyde level dropped to and stabilized at8-10%, as determined by the method disclosed in Formaldehyde, 2nd ed.,J. Frederick Walker, 1953, Reinhold Publishing Co., N.Y., page 383. Atthis point, the solution was cooled to 25 C., the pH adjusted to 6.9-7.1with cone. HCl, and then adjusted to 50% active by the addition of 37parts water.

4 Example 2.--Preparation of methyl carbamate-formaldehyde condensateExample 1 was repeated, using parts of methyl carbamate, 202 parts 37%formaldehyde, and 21 parts water at the end to get a 50% active mix.

Examples 3, 4, 5, and 6.-Pad baths Pad baths were made as follows:

Each of the examples then was made up 400 pounds with water to give 10%concentration of active material.

Each of Examples 3, 4, 5, and 6 was used to impregnate x 80 print cloth(3.75 square yards per pound) and 136 x 64 broadcloth (2.8 square yardsper pound) controlling the impregnation for 80% pickup based on fabricweight. Samples of the cloths were then dried to moisture contents of4.9%, 4.0%, 3.0%, and 2.5% at -110 C. Creases were then pressed into thesamples by pressing with a hand iron at the cotton setting (350- 400 F.)with some additional pressure above the weight of the iron, and thepressed samples were then further processed at 320 F. in a circulatingair oven (2 minutes for Examples 3 and 5, 4 minutes for Examples 4 and6). Other samples were pressed on a hot head press operating at about310-315 F. under 80 p.s.i.g. steam pressure, and then post-cured for 2minutes at 320 F.

All of the cloth samples which retained 4.9% moisture developed a smallbut still noticeable formaldehyde odor on pressing, whereas the othersamples had no odor on pressing. The samples were then given fivehome-style launderings; all of them retained their creases acceptablyexcept the 2.5% samples, which showed a marked loss of crease.

Further extensive testing was done on the product of Example 3. Storagestability on the cloths after drying to 4% moisture was determined byprolonged storage at 70-75" F. and 4065% relative humidity. Samplesstored sixteen weeks still produced results equivalent to freshlyprepared samples, indicating satisfactory longrange stability.

Both impregnated cloths were then tested under varying pressing andcuring conditions, each being pressed for 30 and 60 seconds, and curedfor 2 or 3 minutes; this made a total of four combinations of conditionsfor each of the two cloths. Replicated samples were then given twentyhome-style launderings using ordinary hypochlorite bleach. Observationswere made after 5, 10, 15, and 20 launderings. The samples all showedessentially no loss of crease, and the fiat portions of the launderedcloths were remarkably smooth. Moreover, no damage from the hypochloritewas observed.

Small laboratory runs made with isopropyl carbamate and sec-butylcarbamate gave essential similar results. Moreover, changes in thecarbamate formaldehyde molar ratio over the range 1:2 to 1:3 indicatedthis entire range was useful. Changes were also made in concentrationsof active agent in the pad liquor, and results were essentially whatwould be expected from the smaller or larger concentrations of finishingagent present.

We claim:

1. In the process of producing a cellulose containing fabric capable ofhaving permanent creases made therein by heat and pressure, byimpregnating the fabric with an aqueous dispersion containing anoperative amount of a condensation product of 1 mol of a lower alkylcarbamate and from 2 to 3 mols of formaldehyde, and dry- 5 ing thefabric, the improvement which comprises drying the fabric, attemperatures of from 95 to 150 C., to the point where the fabriccontains from 4.75 to 3.0% moisture.

2. The process of claim 1, in which the alkyl carbamate is ethylcarbamate.

3. The method of producing permanent creases in a structure made from acellulose containing fabric which comprises producing a cellulosecontaining fabric according to the process of claim 1, thereafterworking up the fabric into a structure, ironing creases into the fabricby References Cited UNITED STATES PATENTS 3/1961 Warnock et a1. 8-1163LEON D. ROSDOL, Primary Examiner.

J. D. WELSH, Assistant Examiner.

